Know more

About cookies

What is a "cookie"?

A "cookie" is a piece of information, usually small and identified by a name, which may be sent to your browser by a website you are visiting. Your web browser will store it for a period of time, and send it back to the web server each time you log on again.

Different types of cookies are placed on the sites:

  • Cookies strictly necessary for the proper functioning of the site
  • Cookies deposited by third party sites to improve the interactivity of the site, to collect statistics

Learn more about cookies and how they work

The different types of cookies used on this site

Cookies strictly necessary for the site to function

These cookies allow the main services of the site to function optimally. You can technically block them using your browser settings but your experience on the site may be degraded.

Furthermore, you have the possibility of opposing the use of audience measurement tracers strictly necessary for the functioning and current administration of the website in the cookie management window accessible via the link located in the footer of the site.

Technical cookies

Name of the cookie


Shelf life

CAS and PHP session cookies

Login credentials, session security



Saving your cookie consent choices

12 months

Audience measurement cookies (AT Internet)

Name of the cookie


Shelf life


Trace the visitor's route in order to establish visit statistics.

13 months


Store the anonymous ID of the visitor who starts the first time he visits the site

13 months


Identify the numbers (unique identifiers of a site) seen by the visitor and store the visitor's identifiers.

13 months

About the AT Internet audience measurement tool :

AT Internet's audience measurement tool Analytics is deployed on this site in order to obtain information on visitors' navigation and to improve its use.

The French data protection authority (CNIL) has granted an exemption to AT Internet's Web Analytics cookie. This tool is thus exempt from the collection of the Internet user's consent with regard to the deposit of analytics cookies. However, you can refuse the deposit of these cookies via the cookie management panel.

Good to know:

  • The data collected are not cross-checked with other processing operations
  • The deposited cookie is only used to produce anonymous statistics
  • The cookie does not allow the user's navigation on other sites to be tracked.

Third party cookies to improve the interactivity of the site

This site relies on certain services provided by third parties which allow :

  • to offer interactive content;
  • improve usability and facilitate the sharing of content on social networks;
  • view videos and animated presentations directly on our website;
  • protect form entries from robots;
  • monitor the performance of the site.

These third parties will collect and use your browsing data for their own purposes.

How to accept or reject cookies

When you start browsing an eZpublish site, the appearance of the "cookies" banner allows you to accept or refuse all the cookies we use. This banner will be displayed as long as you have not made a choice, even if you are browsing on another page of the site.

You can change your choices at any time by clicking on the "Cookie Management" link.

You can manage these cookies in your browser. Here are the procedures to follow: Firefox; Chrome; Explorer; Safari; Opera

For more information about the cookies we use, you can contact INRAE's Data Protection Officer by email at or by post at :


24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021

Menu Logo Principal Logo Université Tours Logo CHU Tours Logo CNRS Logo IFCE Logo Région Centre-Val de loire Logo GIS IBiSA

Home page


2D gel
PIXANIM offers 1D/2D electrophoresis and liquid chromatography for the separation and purification of proteins.

Protein extraction

Qualitative and quantitative proteomics requires the use of quality biological samples. The extraction of proteins from organs, tissues, isolated cells or physiological fluids is carried out using appropriate buffers according to the nature of the proteins to be studied (cytosolic, membrane, nuclear proteins, etc.). Extraction buffers at a given pH are composed of mixtures of reducing agents, detergents or even organic solvents. They are generally supplemented with protease inhibitors. Experimental protocols must avoid contamination by nucleic acids, lipids and salts. In general, the protocols must be adapted for each biological model.

2D/1D electrophoresis

2D electrophoresis enables the proteins in a complex mixture to be separated in two stages according to two distinct properties of these molecules: their charge and their relative molecular mass. The first dimension consists of depositing the protein mixture on a polyacrylamide gel containing a stable pH gradient (carrier ampholytes or immobilised gradient). Isoelectrofocusing (IEF) consists of subjecting the proteins to an electic field.
The proteins, amphiphilic molecules (which carry positive and negative charges located on the side chains of the amino acids) are then separated according to their isoelectric point (pI). They migrate until their electric charge is zero. Different types of immobilised pH gradients allow proteins to be separated in the 1st dimension in the extreme acidic or basic pH ranges, or over the whole pH range 3-12. Narrow, overlapping pH gradients break down the pH range 4-7 into a single pH unit (4-5, 5-6, etc.). The number of proteins detected is then doubled. The narrow gradients between pH 7 and 10 remain difficult to use.
Before the 2nd dimension, the IEF gels are re-balanced in order to impregnate the gel with SDS (sodium dodecyl sulphate), a strong acid denaturing detergent, which will give the proteins a negative charge. The SDS interacts with the proteins and gives each one the same charge/mass ratio. Once the IEF gel is saturated with SDS, it is deposited on top of an acrylamide gel so that the molecules are separated according to their apparent mass (kDa). The protein stains are then revealed by different colourings.
Hydrophobic proteins such as membrane proteins are difficult to solubilise. Similarly, very basic proteins, such as histones and ribosomal proteins, are hardly visible on a 2D gel after isoelectrofocusing.
Some classes of proteins encounter some analytical problems with 2D electrophoresis. In particular, two critical steps have been identified: the first dimension of separation (IEF) and transfer to the second dimension. In order to avoid losses of material at these stages, an alternative consists in simply separating the protein mixture of interest by mono-dimensional electrophoresis on acrylamide gel, SDS-PAGE. In the case of complex protein mixtures, a coloured gel strip may contain many proteins. The identification of the proteins present in a band then requires nanoLC-MS/MS (cf bottom-up proteomics).

Liquid chromatography

Chromatography is an analytical technique allowing the separation of the constituents of a mixture, based on the distribution of these constituents between a mobile phase (liquid or gas) and a stationary phase (solid or liquid) with a large contact surface. Liquid-solid chromatography is well suited to the separation of amphiphilic ionised macromolecules such as proteins.